Caption: Mandrill (Mandrillus sphinx) eating a pine branch. The vivid colouration on the male's face is used in threat displays between members of the troop. The females do not have the prominent red stripe on their noses. Mandrill troops usually contain around 50 individuals. They inhabit the forests of western equatorial Africa, but spend most of their time on the ground. They retreat to the trees to sleep at night. Mandrills are omnivorous, eating roots and fruits as well as frogs, lizards and snakes. Mandrills may reach a length of almost a metre.